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Process for the production of difluoromethane

a technology of difluoromethane and vapor phase, which is applied in the direction of physical/chemical process catalysts, halogenated hydrocarbon preparations, metal/metal-oxide/metal-hydroxide catalysts, etc., can solve the problems of low product yield and selectivity of the process for hfc-32 production

Inactive Publication Date: 2005-01-18
ALLIED SIGNAL INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

AI Technical Summary

Benefits of technology

"The present invention provides a method for producing HFC-32, a replacement for environmentally harmful refrigerants, with good yield and selectivity. The process involves contacting HCC-30 and HF in the presence of a fluorination catalyst to produce a product stream of difluoromethane, chlorofluoromethane, hydrogen chloride, dichloromethane, and hydrogen fluoride. The process overcomes problems of previous methods such as low yield and selectivity, and operational difficulties. The invention includes preheating a composition of HF and HCC-30, reacting it in the presence of a fluorination catalyst, and recovering the HFC-32 from the product stream. The process utilizes a continuous recycle stream of the high boiling fraction obtained in a previous step to increase the HF:organics mole ratio and decrease the production of unreacted HCC-30. The ratio of HF to organics should be at least about 25:1. The invention also includes a method for recycling the high boiling fraction obtained in a previous step to increase the yield and selectivity of HFC-32."

Problems solved by technology

In practice, these processes for HFC-32 production suffer from a variety of problems including low product yield and selectivity as well as operational difficulties such as feed decomposition.

Method used

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Examples

Experimental program
Comparison scheme
Effect test

examples 1 and 2

In a ½ inch Monel pipe reactor, about 110 ml Cr2O3 / Al2O3 (40 / 60 wt %) co-extruded catalyst were packed. The catalyst was dried / calcined at about 400° C. for about 16 hours using air at 2-3 liters per minute. Then, the temperature was lowered to 200° C. and air was replaced with nitrogen at about 0.5-1.5 liters per minute. Anhydrous HF was pumped into the reactor at about 1-2 ml / min until exotherm passed through the reactor. Subsequently, temperature was raised at 25° C. every half hour until the temperature was about 350-400° C. and held there for 8 hours. Temperature was then lowered to the desired reaction temperature. HF and HCC-30 were fed into the reactor at a molar ratio of 4:1 (HF: HCC-30). The mixture of HF and HCC-30 passed through two preheaters, the first of which was at about 100-185° C. and the second at about 200-275° C. The pressure was 50 psig and reactor temperature was 275° C. for Example 1 and 300° C. for Example 2. For Example 1, contact time was 16 seconds resul...

examples 3-6

In the pipe reactor of Examples 1 and 2, about 100-110 ml Cr2O3 / Al2O3 catalyst of 78 / 22 weight percent ratio was packed. The catalyst was dried / calcined and HF-treated using the same procedure as for Examples 1 & 2. HF and HCC-30 were fed into the reactor at a 4:1 (BF / HCC-30) ratio. A mixture of HF and HCC-30 was passed through the same preheaters indicated in Examples 1 & 2. Pressures, contact times, and the results are shown on Table II.

TABLE IIExample 3Example 4Example 5Example 6CatalystCr2O3 / Al2O3Cr2O3 / Al2O3Cr2O3 / Al2O3Cr2O3 / Al2O3(78 / 22 wt %)(78 / 22 wt %)(78 / 22 wt %)(78 / 22 wt %)Pressure (psig)50200225225HF / CH2Cl2 4444mole ratioTemperature275275275275(° C.)Contact Time11364026(sec)Conversion71707061(% CH2Cl2)Selectivity:HFC-3282818177HCFC-3118191923HCC-400.050.050.050.05Productivity(lbs / hr / ft3):HFC-3212121215

example 7

A 4 inch diameter Monel 400 reactor was charged with 4 liters of chromium oxide catalyst. The catalyst was dried under 20 slpm nitrogen flow at a temperature of 350° C. for 8 hours. After reducing the catalyst bed temperature to 250° C., anhydrous HF was added to the flowing nitrogen at a flow rate of 0.2 lbs / hr. The HF flow rate was gradually increased to 1.0 lb / hr and the temperature increased to 350° C. and held for 4 hours. The catalyst bed temperature was then decreased to 250° C. and chlorine introduced to the HF / N2 mixture at a rate of 500 sccm for a period of 24 hours.

After this pretreatment procedure, the chlorine and nitrogen flows were discontinued and HCC-30 was mixed with HF and passed though a preheater at 185° C. The vaporized HCC-30 and HF mixture was fed to the reactor at a pressure of 45 psig. the effluent from the reactor was quenched using a heat exchanger and fed into a distillation column maintained at 50 psig. The low boiling distillation components, HCFC-31, ...

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Abstract

The present invention provides a vapor phase process for the production of difluoromethane, HFC-32. The process of this invention provides for the preparation of HFC-32 by a process that exhibits both good product yield and selectivity.

Description

FIELD OF THE INVENTIONThe present invention relates to a vapor phase process for the production of difluoromethane, HFC-32. In particular, this invention provides a process for the preparation of HFC-32 that exhibits good product yield and selectivity.BACKGROUND OF THE INVENTIONIt is well known in the art that HFC-32 may be used as a replacement for environmentally disadvantageous chlorofluorocarbon refrigerants, blowing agents, and aerosol propellants. A variety of methods for the vapor phase production of HFC-32 are known.For example, U.S. Pat. No. 2,745,886 discloses a vapor phase process for fluorinating a variety of halohydrocarbons including methylene chloride, HCC-30, which process utilizes a hydrated chromium fluoride catalyst activated with oxygen. Similarly, U.S. Pat. No. 2,744,148 discloses a halohydrocarbon fluorination process in which an HF-activated alumina catalyst is used.U.S. Pat. No. 3,862,995 discloses the vapor phase production of HFC-32 by reacting vinyl chlori...

Claims

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Application Information

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Patent Type & Authority Patents(United States)
IPC IPC(8): C07C17/00C07C17/20C07B61/00C07C17/383C07C19/08B01J23/26
CPCC07C17/206C07C19/08C07C17/20
Inventor CLEMMER, PAUL GENESMITH, ADDISON MILESTUNG, HSUEH SUNGBASS, JOHN STEPHEN
Owner ALLIED SIGNAL INC
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